components/network_hints/renderer/renderer_dns_prefetch.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // See header file for description of RendererDnsPrefetch class
   6
   7 #include "components/network_hints/renderer/renderer_dns_prefetch.h"
   8
   9 #include <ctype.h>
  10
  11 #include "base/bind.h"
  12 #include "base/location.h"
  13 #include "base/logging.h"
  14 #include "base/message_loop/message_loop.h"
  15 #include "components/network_hints/common/network_hints_common.h"
  16 #include "components/network_hints/common/network_hints_messages.h"
  17 #include "components/network_hints/renderer/dns_prefetch_queue.h"
  18 #include "content/public/renderer/render_thread.h"
  19
  20 using content::RenderThread;
  21
  22 namespace network_hints {
  23
  24 RendererDnsPrefetch::RendererDnsPrefetch()
  25     : c_string_queue_(1000),
  26       weak_factory_(this) {
  27   Reset();
  28 }
  29
  30 RendererDnsPrefetch::~RendererDnsPrefetch() {
  31 }
  32
  33 void RendererDnsPrefetch::Reset() {
  34   domain_map_.clear();
  35   c_string_queue_.Clear();
  36   buffer_full_discard_count_ = 0;
  37   numeric_ip_discard_count_ = 0;
  38   new_name_count_ = 0;
  39 }
  40
  41 // Push names into queue quickly!
  42 void RendererDnsPrefetch::Resolve(const char* name, size_t length) {
  43   if (!length)
  44     return;  // Don't store empty strings in buffer.
  45   if (is_numeric_ip(name, length))
  46     return;  // Numeric IPs have no DNS lookup significance.
  47
  48   size_t old_size =  c_string_queue_.Size();
  49   DnsQueue::PushResult result = c_string_queue_.Push(name, length);
  50   if (DnsQueue::SUCCESSFUL_PUSH == result) {
  51     if (1 == c_string_queue_.Size()) {
  52       DCHECK_EQ(old_size, 0u);
  53       if (0 != old_size)
  54         return;  // Overkill safety net: Don't send too many InvokeLater's.
  55       weak_factory_.InvalidateWeakPtrs();
  56       RenderThread::Get()->GetTaskRunner()->PostDelayedTask(
  57           FROM_HERE, base::Bind(&RendererDnsPrefetch::SubmitHostnames,
  58                                 weak_factory_.GetWeakPtr()),
  59           base::TimeDelta::FromMilliseconds(10));
  60     }
  61     return;
  62   }
  63   if (DnsQueue::OVERFLOW_PUSH == result) {
  64     ++buffer_full_discard_count_;
  65     return;
  66   }
  67   DCHECK(DnsQueue::REDUNDANT_PUSH == result);
  68 }
  69
  70 // Extract data from the Queue, and then send it off the the Browser process
  71 // to be resolved.
  72 void RendererDnsPrefetch::SubmitHostnames() {
  73   // Get all names out of the C_string_queue (into our map)
  74   ExtractBufferedNames();
  75   // TBD: IT could be that we should only extract about as many names as we are
  76   // going to send to the browser.  That would cause a "silly" page with a TON
  77   // of URLs to start to overrun the DnsQueue, which will cause the names to
  78   // be dropped (not stored in the queue).  By fetching ALL names, we are
  79   // taking on a lot of work, which may take a long time to process... perhaps
  80   // longer than the page may be visible!?!?!  If we implement a better
  81   // mechanism for doing domain_map.clear() (see end of this method), then
  82   // we'd automatically flush such pending work from a ridiculously link-filled
  83   // page.
  84
  85   // Don't overload the browser DNS lookup facility, or take too long here,
  86   // by only sending off kMaxDnsHostnamesPerRequest names to the Browser.
  87   // This will help to avoid overloads when a page has a TON of links.
  88   DnsPrefetchNames(kMaxDnsHostnamesPerRequest);
  89   if (new_name_count_ > 0 || 0 < c_string_queue_.Size()) {
  90     weak_factory_.InvalidateWeakPtrs();
  91     RenderThread::Get()->GetTaskRunner()->PostDelayedTask(
  92         FROM_HERE, base::Bind(&RendererDnsPrefetch::SubmitHostnames,
  93                               weak_factory_.GetWeakPtr()),
  94         base::TimeDelta::FromMilliseconds(10));
  95   } else {
  96     // TODO(JAR): Should we only clear the map when we navigate, or reload?
  97     domain_map_.clear();
  98   }
  99 }
 100
 101 // Pull some hostnames from the queue, and add them to our map.
 102 void RendererDnsPrefetch::ExtractBufferedNames(size_t size_goal) {
 103   size_t count(0);  // Number of entries to find (0 means find all).
 104   if (size_goal > 0) {
 105     if (size_goal <= domain_map_.size())
 106       return;  // Size goal was met.
 107     count = size_goal - domain_map_.size();
 108   }
 109
 110   std::string name;
 111   while (c_string_queue_.Pop(&name)) {
 112     DCHECK_NE(name.size(), 0u);
 113     // We don't put numeric IP names into buffer.
 114     DCHECK(!is_numeric_ip(name.c_str(), name.size()));
 115     DomainUseMap::iterator it;
 116     it = domain_map_.find(name);
 117     if (domain_map_.end() == it) {
 118       domain_map_[name] = kPending;
 119       ++new_name_count_;
 120       if (0 == count) continue;  // Until buffer is empty.
 121       if (1 == count) break;  // We found size_goal.
 122       DCHECK_GT(count, 1u);
 123       --count;
 124     } else {
 125       DCHECK(kPending == it->second || kLookupRequested == it->second);
 126     }
 127   }
 128 }
 129
 130 void RendererDnsPrefetch::DnsPrefetchNames(size_t max_count) {
 131   // We are on the renderer thread, and just need to send things to the browser.
 132   NameList names;
 133   for (DomainUseMap::iterator it = domain_map_.begin();
 134     it != domain_map_.end();
 135     ++it) {
 136     if (0 == (it->second & kLookupRequested)) {
 137       it->second |= kLookupRequested;
 138       names.push_back(it->first);
 139       if (0 == max_count) continue;  // Get all, independent of count.
 140       if (1 == max_count) break;
 141       --max_count;
 142       DCHECK_GE(max_count, 1u);
 143     }
 144   }
 145   DCHECK_GE(new_name_count_, names.size());
 146   new_name_count_ -= names.size();
 147
 148   network_hints::LookupRequest request;
 149   request.hostname_list = names;
 150   RenderThread::Get()->Send(new NetworkHintsMsg_DNSPrefetch(request));
 151 }
 152
 153 // is_numeric_ip() checks to see if all characters in name are either numeric,
 154 // or dots.  Such a name will not actually be passed to DNS, as it is an IP
 155 // address.
 156 bool RendererDnsPrefetch::is_numeric_ip(const char* name, size_t length) {
 157   // Scan for a character outside our lookup list.
 158   while (length-- > 0) {
 159     if (!isdigit(*name) && '.' != *name)
 160       return false;
 161     ++name;
 162   }
 163   return true;
 164 }
 165
 166 }  // namespace predictor